Ultra-thin ceramic coating on separator for batteries

ABSTRACT

Implementations of the present disclosure generally relate to separators, high performance electrochemical devices, such as, batteries and capacitors, including the aforementioned separators, systems and methods for fabricating the same. In one implementation, a separator is provided. The separator comprises a polymer substrate, capable of conducting ions, having a first surface and a second surface opposing the first surface. The separator further comprises a first ceramic-containing layer, capable of conducting ions, formed on the first surface. The first ceramic-containing layer has a thickness in a range from about 1,000 nanometers to about 5,000 nanometers. The separator further comprises a second ceramic-containing layer, capable of conducting ions, formed on the second surface. The second ceramic-containing layer is a binder-free ceramic-containing layer and has a thickness in a range from about 1 nanometer to about 1,000 nanometers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/479,988, filed Jul. 23, 2019, which is a 371 National Stage ofInternational Appl. No. PCT/CN2018/101525, filed Aug. 21, 2018, whichare herein incorporated by reference in their entirety.

BACKGROUND Field

Implementations of the present disclosure generally relate toseparators, high performance electrochemical devices, such as batteriesand capacitors, including the aforementioned separators, systems andmethods for fabricating the same.

Description of the Related Art

Fast-charging, high-capacity energy storage devices, such as capacitorsand lithium-ion (Li-ion) batteries, are used in a growing number ofapplications, including portable electronics, medical, transportation,grid-connected large energy storage, renewable energy storage, anduninterruptible power supply (UPS).

Li-ion batteries typically include an anode electrode, a cathodeelectrode, and a separator positioned between the anode electrode andthe cathode electrode. The separator is an electronic insulator, whichprovides physical and electrical separation between the cathode and theanode electrodes. The separator is typically made from micro-porouspolyethylene and polyolefin. During electrochemical reactions, forexample, charging and discharging, lithium ions are transported throughthe pores in the separator between the two electrodes via anelectrolyte. Thus, high porosity helps increase ionic conductivity.However, some high porosity separators are susceptible to electricalshorts when lithium dendrites formed during cycling create shortsbetween the electrodes.

Currently, battery cell manufacturers purchase separators, which arethen laminated together with anode and cathode electrodes in separateprocessing steps. Other separators are typically made by wet or dryextrusion of a polymer and then stretched to produce holes (tears) inthe polymer material. The separator is generally one of the mostexpensive components in the Li-ion battery and accounts for over 20% ofthe material cost in battery cells.

For most energy storage applications, the charge time and capacity ofenergy storage devices are parameters of interest. In addition, thesize, weight, and/or expense of such energy storage devices can besignificant limitations. The use of currently available separators has anumber of drawbacks. Namely, such available materials limit the minimumsize of the electrodes constructed from such materials, suffer fromelectrical shorts, involve complex manufacturing methods, and expensivematerials. Further, current separator designs often suffer from lithiumdendrite growth, which may lead to short-circuits.

Accordingly, there is a need in the art for faster charging, highercapacity energy storage devices with separators that are smaller,lighter, and can be more cost effectively manufactured.

SUMMARY

Implementations of the present disclosure generally relate toseparators, high performance electrochemical devices, such as, batteriesand capacitors, including the aforementioned separators, systems andmethods for fabricating the same. In one implementation, a separator isprovided. The separator comprises a polymer substrate, capable ofconducting ions, having a first surface and a second surface opposingthe first surface. The separator further comprises a firstceramic-containing layer, capable of conducting ions, formed on thefirst surface. The first ceramic-containing layer has a thickness in arange from about 1,000 nanometers to about 5,000 nanometers. Theseparator further comprises a second ceramic-containing layer, capableof conducting ions, formed on the second surface. The secondceramic-containing layer is a binder-free ceramic-containing layer andhas a thickness in a range from about 1 nanometer to about 1,000nanometers.

In another implementation, a battery is provided. The battery comprisesan anode containing at least one of lithium metal, lithium-alloy,graphite, silicon-containing graphite, nickel, copper, tin, indium,silicon, or combinations thereof. The battery further comprises acathode. The battery further comprises a separator disposed between theanode and the cathode. The separator comprises a polymer substrate,capable of conducting ions, having a first surface and a second surfaceopposing the first surface. The separator further comprises a firstceramic-containing layer, capable of conducting ions, formed on thefirst surface. The first ceramic-containing layer has a thickness in arange from about 1,000 nanometers to about 5,000 nanometers. Theseparator further comprises a second ceramic-containing layer, capableof conducting ions, formed on the second surface. The secondceramic-containing layer is a binder-free ceramic-containing layer andhas a thickness in a range from about 1 nanometer to about 1,000nanometers.

In yet another implementation, a method of forming a separator for abattery is provided. The method comprises exposing a material to bedeposited on a microporous ion-conducting polymeric layer positioned ina processing region to an evaporation process. The microporousion-conducting polymeric layer has a first surface, a second surfaceopposing the first surface, and a first ceramic-containing layer,capable of conducting ions, formed on the first surface. The firstceramic-containing layer has a thickness in a range from about 1,000nanometers to about 5,000 nanometers. The method further comprisesreacting the evaporated material with a reactive gas and/or plasma todeposit a second ceramic-containing layer, capable of conducting ions,on the second surface of the microporous ion-conducting polymeric layer.The second ceramic-containing layer is a binder-free ceramic-containinglayer and has a thickness in a range from about 1 nanometer to about1,000 nanometers.

In yet another implementation, a method of forming a separator for abattery is provided. The method comprises exposing a first material tobe deposited on a microporous ion-conducting polymeric layer positionedin a processing region to an evaporation process. The microporousion-conducting polymeric layer has a first surface, a second surfaceopposing the first surface, and a first ceramic-containing layer,capable of conducting ions, formed on the first surface. The firstceramic-containing layer has a thickness in a range from about 1,000nanometers to about 5,000 nanometers. The method further comprisesreacting the evaporated first material with a reactive gas and/or plasmato deposit a second ceramic-containing layer, capable of conductingions, on the second surface of the microporous ion-conducting polymericlayer. The second ceramic-containing layer is a binder-freeceramic-containing layer and has a thickness in a range from about 1nanometer to about 100 nanometers. The method further comprises exposingthe microporous ion-conducting polymeric layer to a first coolingprocess. The method further comprises reacting an evaporated secondmaterial with a reactive gas and/or plasma to deposit a thirdceramic-containing layer, capable of conducting ions, on the secondceramic-containing layer. The third ceramic-containing layer is abinder-free ceramic-containing layer and has a thickness in a range fromabout 1 nanometer to about 100 nanometers.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe implementations, briefly summarized above, may be had by referenceto implementations, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical implementations of this disclosure and aretherefore not to be considered limiting of its scope, for the disclosuremay admit to other equally effective implementations.

FIG. 1 illustrates a cross-sectional view of one implementation of acell structure formed according to one or more implementations describedherein;

FIG. 2 illustrates a cross-sectional view of a ceramic-coated separatorformed according to one or more implementations described herein;

FIG. 3 illustrates a process flow chart summarizing one implementationof a method for forming an electrode structure according toimplementations described herein;

FIG. 4A illustrates a cross-sectional view of another ceramic-coatedseparator formed according to one or more implementations describedherein;

FIG. 4B illustrates an exploded cross-sectional view of a portion of theceramic-coated separator depicted in FIG. 4A;

FIG. 5 illustrates a process flow chart summarizing one implementationof another method for forming a ceramic-coating separator according toimplementations described herein;

FIG. 6A illustrates a schematic top view of an evaporation apparatus forforming a ceramic-coated separator according to implementationsdescribed herein;

FIG. 6B illustrates a schematic front view of the evaporation apparatusshown in FIG. 6A; and

FIG. 6C illustrates a schematic top view of the evaporation apparatusshown in FIG. 6A.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneimplementation may be beneficially incorporated in other implementationswithout further recitation.

DETAILED DESCRIPTION

The following disclosure describes separators, high performanceelectrochemical cells and batteries including the aforementionedseparators, systems and methods for fabricating the same. Certaindetails are set forth in the following description and in FIGS. 1-6C toprovide a thorough understanding of various implementations of thedisclosure. Other details describing well-known structures and systemsoften associated with electrochemical cells and batteries are not setforth in the following disclosure to avoid unnecessarily obscuring thedescription of the various implementations.

Many of the details, dimensions, angles and other features shown in theFigures are merely illustrative of particular implementations.Accordingly, other implementations can have other details, components,dimensions, angles and features without departing from the spirit orscope of the present disclosure. In addition, further implementations ofthe disclosure can be practiced without several of the details describedbelow.

Implementations described herein will be described below in reference toa high rate evaporation process that can be carried out using aroll-to-roll coating system, such as TopMet™, SmartWeb™, TopBeam™ all ofwhich are available from Applied Materials, Inc. of Santa Clara,California. Other tools capable of performing high rate evaporationprocesses may also be adapted to benefit from the implementationsdescribed herein. In addition, any system enabling high rate evaporationprocesses described herein can be used to advantage. The apparatusdescription described herein is illustrative and should not be construedor interpreted as limiting the scope of the implementations describedherein. It should also be understood that although described as aroll-to-roll process, the implementations described herein may beperformed on discrete polymer substrates.

The currently available generation of batteries, especially Li-ionbatteries, use porous polymer separators, which are susceptible tothermal shrinkage and may short-circuit between positive and negativeelectrodes or the corresponding current collectors. A ceramic coating onthe separator helps to inhibit direct contact between electrodes andhelps to prevent potential dendrite growth associated with lithiummetal. Current state of the art ceramic coating is performed using wetcoating (e.g., slot-die techniques) of ceramic particles dispersed in apolymeric binder to make the composite and a solvent is used to make theslurry. The thickness of the ceramic coating is normally around threemicrons including randomly oriented dielectric material bound togetherby a polymer leading to a random pore structure. The existing ceramicparticle coating method has difficulty in reducing tortuosity due tothis random orientation of ceramic particles. Further, it is difficultto reduce the thickness of current ceramic coatings using current wetcoating methods. In order to compensate for the increased surface areaof finer ceramic powder particles current wet coating methods involveincreased amounts of both binder and solvent to decrease the viscosityof the slurry. Thus, the current wet coating methods suffer from severalproblems.

From a manufacturing standpoint, ceramic coating via dry methods isideal from both a cost and performance point of view. However, drymethods such as physical vapor deposition (PVD) are performed atelevated processing temperatures. Elevated processing temperatures incombination with the decreasing thickness of polymer separators leads toheat induced damage such as melting or creating wrinkles in the polymerseparator. In addition, thinner polymer separators often lack themechanical integrity for current roll-to-roll processing systems.

In the present disclosure, a thin polymer separator stack is provided.The thin polymer separator stack includes an ultra-thin ceramic-coatingformed on a first side of front side of the thin polymer separator,which suppresses thermal shrinkage while maintaining the desired ionicconductivity. The ultra-thin ceramic-coating may be deposited using PVDtechniques at elevated temperatures. The ultra-thin ceramic coating mayhave a thickness in a range from about 0.05 to about 0.5 microns. Thethin polymer separator stack further includes a thick ceramic coatingformed on a second side or backside of the of the thin polymerseparator, which provides mechanical stability while maintaining thedesired ionic conductivity. The thick ceramic coating may be depositedusing wet-coating techniques. The thick ceramic coating may have athickness in a range from about 1 micron to about 5 microns. Thus, thethin polymer separator stack includes the benefit of reduced thermalshrinkage with improved mechanical stability while maintaining desiredionic conductivity at a decreased separator thickness (e.g., 12 micronsor less).

FIG. 1 illustrates an example of a cell structure 100 having aceramic-coated separator according to implementations of the presentdisclosure. The cell structure 100 has a positive current collector 110,a positive electrode 120, a ceramic-coated separator 130, a negativeelectrode 140 and a negative current collector 150. Note in FIG. 1 thatthe current collectors are shown to extend beyond the stack, although itis not necessary for the current collectors to extend beyond the stack,the portions extending beyond the stack may be used as tabs. The cellstructure 100, even though shown as a planar structure, may also beformed into a cylinder by rolling the stack of layers; furthermore,other cell configurations (e.g., prismatic cells, button cells) may beformed.

The current collectors 110, 150, on the positive electrode 120 and thenegative electrode 140, respectively, can be identical or differentelectronic conductors. Examples of metals that the current collectors110, 150 may be comprised of include aluminum (Al), copper (Cu), zinc(Zn), nickel (Ni), cobalt (Co), tin (Sn), silicon (Si), manganese (Mn),magnesium (Mg), alloys thereof, and combinations thereof. In oneimplementation, the current collector 110 comprises aluminum and thecurrent collector 150 comprises copper.

The negative electrode 140 or anode may be any material compatible withthe positive electrode 120. The negative electrode 140 may have anenergy capacity greater than or equal to 372 mAh/g, preferably≥700mAh/g, and most preferably≥1,000 mAh/g. The negative electrode 140 maybe constructed from a graphite, silicon-containing graphite (e.g.,silicon (<5%) blended graphite), a lithium metal foil or a lithium alloyfoil (e.g. lithium aluminum alloys), or a mixture of a lithium metaland/or lithium alloy and materials such as carbon (e.g. coke, graphite),nickel, copper, tin, indium, silicon, oxides thereof, or combinationsthereof.

The positive electrode 120 or cathode may be any material compatiblewith the anode and may include an intercalation compound, an insertioncompound, or an electrochemically active polymer. Suitable intercalationmaterials include, for example, lithium-containing metal oxides, MoS₂,FeS₂, MnO₂, TiS₂, NbSe₃, LiCoO₂, LiNiO₂, LiMnO₂, LiMn₂O₄, V₆O₁₃ andV₂O₅. Suitable lithium-containing oxides include layered, such aslithium cobalt oxide (LiCoO₂), or mixed metal oxides, such asLiNixCo_(1-2x)MnO₂, LiNiMnCoO₂ (“NMC”), LiNi_(0.5)Mn_(1.5)O₄,Li(Ni_(0.8)Co_(0.15)Al_(0.05))O₂, LiMn₂O₄, and doped lithium richlayered-layered materials, wherein x is zero or a non-zero number.Suitable phosphates include iron olivine (LiFePO₄) and it's variants(such as LiFe_((1-x))Mg_(x)PO₄), LiMoPO₄, LiCoPO₄, LiNiPO₄, Li₃V₂(PO₄)₃,LiVOPO₄, LiMP₂O₇, or LiFe_(1.5)P₂O₇, wherein x is zero or a non-zeronumber. Suitable fluorophosphates include LiVPO₄F, LiAlPO₄F,Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂, Li₂CoPO₄F, or Li₂NiPO₄F. Suitable silicatesmay be Li₂FeSiO₄, Li₂MnSiO₄, or Li₂VOSiO₄. An exemplary non-lithiumcompound is Na₅V₂(PO₄)₂F₃.

Electrolytes infused in cell components 120, 130 and 140 can becomprised of a liquid/gel or a solid polymer and may be different ineach. Any suitable electrolyte may be used. In some implementations, theelectrolyte primarily includes a salt and a medium (e.g., in a liquidelectrolyte, the medium may be referred to as a solvent; in a gelelectrolyte, the medium may be a polymer matrix). The salt may be alithium salt. The lithium salt may include, for example, LiPF₆, LiAsF₆,LiCF₃SO₃, LiN(CF₃SO₃)₃, LiBF₆, and LiClO₄, BETTE electrolyte(commercially available from 3M Corp. of Minneapolis, Minn.) andcombinations thereof.

FIG. 2 illustrates a cross-sectional view of the ceramic-coatedseparator 130 formed according to one or more implementations describedherein. The ceramic-coated separator 130 includes a porous (e.g.,microporous) polymeric substrate 131 capable of conducting ions (e.g., aseparator film). The porous polymeric substrate 131 has a first surface132 and a second surface 134 opposite the first surface 132. A firstceramic-containing layer 136, capable of conducting ions, is formed onat least a portion of the first surface 132 of the porous polymericsubstrate 131. A second ceramic-containing layer 138 (e.g., ultra-thinceramic coating), capable of conducting ions, is formed on at least aportion of the second surface 134 of the porous polymeric substrate 131.The first ceramic-containing layer 136 has a thickness greater than athickness of the second ceramic-containing layer 138.

In some implementations, the porous polymeric substrate 131 does notneed to be ion-conducting, however, once filled with electrolyte(liquid, gel, solid, combination etc.), the combination of poroussubstrate and electrolyte is ion-conducting. The firstceramic-containing layer 136 and the second ceramic-containing layer 138are, at least, adapted for preventing electronic shorting (e.g. director physical contact of the anode and the cathode) and blocking dendritegrowth. The porous polymeric substrate 131 may be, at least, adapted forblocking (or shutting down) ionic conductivity (or flow) between theanode and the cathode during the event of thermal runaway. The firstceramic-containing layer 136 and the second ceramic-containing layer 138of the ceramic-coated separator 130 should be sufficiently conductive toallow ionic flow between the anode and cathode, so that the cellstructure 100 generates current in desired quantities. As discussedherein, in one implementation, the second ceramic-containing layer 138is formed on the porous polymeric substrate 131 using evaporationtechniques.

In one implementation, the porous polymeric substrate 131 is amicroporous ion-conducting polymeric substrate. In one implementation,the porous polymeric substrate 131 is a multi-layer polymeric substrate.In some implementations, the porous polymeric substrate 131 is selectedfrom any commercially available polymeric microporous membranes (e.g.,single or multi-ply), for example, those products produced by producedby Polypore (Celgard Inc., of Charlotte, N.C.), Toray Tonen (Batteryseparator film (BSF)), SK Energy (lithium ion battery separator (LiBS),Evonik industries (SEPARION® ceramic separator membrane), Asahi Kasei(Hipore™ polyolefin flat film membrane), DuPont (Energain®), etc. Insome implementations, the porous polymeric substrate 131 has a porosityin the range of 20 to 80% (e.g., in the range of 28 to 60%). In someimplementations, the porous polymeric substrate 131 has an average poresize in the range of 0.02 to 5 microns (e.g., 0.08 to 2 microns). Insome implementations, the porous polymeric substrate 131 has a GurleyNumber in the range of 15 to 150 seconds (Gurley Number refers to thetime it takes for 10 cc of air at 12.2 inches of water to pass throughone square inch of membrane). In some implementations, the porouspolymeric substrate 131 comprises a polyolefin polymer. Examples ofsuitable polyolefin polymers include polypropylene, polyethylene, orcombinations thereof. In some implementations, the porous polymericsubstrate 131 is a polyolefenic membrane. In some implementation, thepolyolefinic membrane is a polyethylene membrane or a polypropylenemembrane.

In one implementation, the porous polymeric substrate 131 has athickness “T₁” in a range from about 1 micron to about 50 microns, forexample, in a range from about 3 microns to about 25 microns; in a rangefrom about 7 microns to about 12 microns; or in a range from about 14microns to about 18 microns.

The first ceramic-containing layer 136 provides mechanical support forthe porous polymeric substrate 131. It has been found by the inventorsthat inclusion of the first ceramic-containing layer 136 reduces thermalshrinkage of the porous polymeric substrate 131 during processing atelevated temperatures. Thus, including the first ceramic-containinglayer 136 allows for the processing of thinner separator materials atelevated temperatures.

The first ceramic-containing layer 136 includes one or more ceramicmaterials. The ceramic material may be an oxide. In one implementation,the first ceramic-containing layer 136 includes a material selectedfrom, for example, aluminum oxide (Al₂O₃), AlO_(x), AlO_(x)N_(y), AlN(aluminum deposited in a nitrogen environment), aluminum hydroxide oxide((AlO(OH)) (e.g., diaspore ((α-AlO(OH))), boehmite (

-AlO(OH)), or akdalaite (5Al₂O₃·H₂O)), calcium carbonate (CaCO₃),titanium dioxide (TiO₂), SiS₂, SiPO₄, silicon oxide (SiO₂), zirconiumoxide (ZrO₂), hafnium oxide (HfO₂), MgO, TiO₂, Ta₂O₅, Nb₂O₅, LiAlO₂,BaTiO₃, BN, ion-conducting garnet, ion-conducting perovskite,ion-conducting anti-perovskites, porous glass ceramic, and the like, orcombinations thereof. In one implementation, the firstceramic-containing layer 136 comprises a combination of AlO_(x) andAl₂O₃. In one implementation, the first ceramic-containing layer 136comprises a material selected from the group comprising, consisting of,or consisting essentially of porous aluminum oxide, porous-ZrO₂,porous-HfO₂, porous-SiO₂, porous-MgO, porous-TiO₂, porous-Ta₂O₅,porous-Nb₂O₅, porous-LiAlO₂, porous-BaTiO₃, ion-conducting garnet,anti-ion-conducting perovskites, porous glass dielectric, orcombinations thereof. In one implementation, the firstceramic-containing layer 136 contains a binder material. In someimplementations, the first ceramic-containing layer 136 is a porousaluminum oxide layer. Any suitable deposition technique, which achievesthe desired ion-conductivity, mechanical integrity, and thickness of thefirst ceramic-containing layer 136 may be used to form the firstceramic-containing layer 136. Suitable techniques include slurrydeposition techniques or wet coating techniques such as slot-dietechniques and doctor blade techniques. In one implementation, the firstceramic-containing layer 136 is deposited using ceramic particlesdispersed in a polymeric binder to make the composite and a solvent tomake the slurry. In one implementation, the first ceramic-containinglayer 136 and the porous polymeric substrate 131 are prefabricated andsupplied together.

In one implementation, the first ceramic-containing layer 136 has athickness “T₂” in a range from about 1,000 nanometers to about 5,000nanometers, for example, in a range from about 1,000 nanometers to about3,000 nanometers; or in a range from about 1,000 nanometers to about2,000 nanometers.

The second ceramic-containing layer 138 includes one or more ceramicmaterials. The ceramic material may be an oxide. In one implementation,the second ceramic-containing layer 138 includes a material selectedfrom, for example, aluminum oxide (Al₂O₃), AlO_(x), AlO_(x)N_(y), AlN(aluminum deposited in a nitrogen environment), aluminum hydroxide oxide((AlO(OH)) (e.g., diaspore ((α-AlO(OH))), boehmite (

-AlO(OH)), or akdalaite (5Al₂O₃·H₂O)), calcium carbonate (CaCO₃),titanium dioxide (TiO₂), SiS₂, SiPO₄, silicon oxide (SiO₂), zirconiumoxide (ZrO₂), hafnium oxide (HfO₂), MgO, TiO₂, Ta₂O₅, Nb₂O₅, LiAlO₂,BaTiO₃, BN, ion-conducting garnet, ion-conducting perovskite,ion-conducting anti-perovskites, porous glass ceramic, and the like, orcombinations thereof. In one implementation, the firstceramic-containing layer 136 comprises a combination of AlO_(x) andAl₂O₃. In one implementation, the second ceramic-containing layer 138includes a material selected from the group comprising, consisting of,or consisting essentially of porous aluminum oxide, porous-ZrO₂,porous-HfO₂, porous-SiO₂, porous-MgO, porous-TiO₂, porous-Ta₂O₅,porous-Nb₂O₅, porous-LiAlO₂, porous-BaTiO₃, ion-conducting garnet,anti-ion-conducting perovskites, porous glass dielectric, orcombinations thereof. The second ceramic-containing layer 138 is abinder-free dielectric layer. In some implementations, the secondceramic-containing layer 138 is a porous aluminum oxide layer. Thesecond ceramic-containing layer 138 is typically deposited usingevaporation techniques as described herein.

In one implementation, the second ceramic-containing layer 138 has athickness “T₃” in a range from about 1 nanometer to about 1,000nanometers, for example, in a range from about 50 nanometers to about500 nanometers; or in a range from about 50 nanometers to about 200nanometers.

In some implementations, the second ceramic-containing layer 138includes a plurality of dielectric columnar projections. The dielectriccolumnar shaped projections may have a diameter that expands from thebottom (e.g., where the columnar shaped projection contacts the poroussubstrate) of the columnar shaped projection to a top of the columnarshaped projection. The dielectric columnar projections typicallycomprise dielectric grains. Nano-structured contours or channels aretypically formed between the dielectric grains.

In some implementations, the second ceramic-containing layer 138 maycomprise one or more of various forms of porosities. In someimplementations, the columnar projections of the secondceramic-containing layer 138 form a nano-porous structure between thecolumnar projections of ceramic material. In one implementation, thenano-porous structure may have a plurality of nano-pores that are sizedto have an average pore size or diameter less than about 10 nanometers(e.g., from about 1 nanometer to about 10 nanometers; from about 3nanometers to about 5 nanometers). In another implementation, thenano-porous structure may have a plurality of nano-pores that are sizedto have an average pore size or diameter less than about 5 nanometers.In one implementation, the nano-porous structure has a plurality ofnano-pores having a diameter ranging from about 1 nanometer to about 20nanometers (e.g., from about 2 nanometers to about 15 nanometers; orfrom about 5 nanometers to about 10 nanometers). The nano-porousstructure yields a significant increase in the surface area of thesecond ceramic-containing layer 138. The pores of the nano-porousstructure can act as liquid electrolyte reservoir and provides excesssurface area for ion-conductivity.

In one implementation, the first ceramic-containing layer 136 and thesecond ceramic-containing layer 138 include the same ceramic material.In another implementation, the first ceramic-containing layer 136 andthe second ceramic-containing layer 138 include different ceramicmaterials.

FIG. 3 illustrates a process flow chart summarizing one implementationof a method 300 for forming a ceramic-coated separator according toimplementations described herein. The ceramic-coated separator may bethe ceramic-coated separator 130 depicted in FIG. 1 and FIG. 2 .

At operation 310, a porous polymeric substrate, such as the porouspolymeric substrate 131, having a first ceramic-containing layer, suchas the first ceramic-containing layer 136, formed on a first surface,such as the first surface 132 of the porous polymeric substrate isprovided. In one implementation, the first ceramic-containing layer 136formed on the porous polymeric substrate 131 is prefabricated andsupplied together. In another implementation, the firstceramic-containing layer 136 is formed on the porous polymeric substrate131 using a slurry deposition process.

At operation 320, the porous polymeric substrate 131 having the firstceramic-containing layer 136 formed thereon is optionally exposed to acooling process. In one implementation, the porous polymeric substrate131 may be cooled to a temperature between −20 degrees Celsius and roomtemperature (i.e., 20 to 22 degrees Celsius) (e.g., −10 degrees Celsiusand 0 degrees Celsius). In some implementations, the porous polymericsubstrate 131 may be cooled by cooling the processing drum over whichthe microporous ion-conducting polymeric substrate travels over duringprocessing. Other active cooling means may be used to cool themicroporous ion-conducting polymeric substrate. During the evaporationprocess, the porous polymeric substrate 131 may be exposed totemperatures in excess of 1,000 degrees Celsius thus it is beneficial tocool the porous polymeric substrate 131 prior to the evaporation processof operation 330.

At operation 330, the material to be deposited on a second surface ofthe porous polymeric substrate 131 is exposed to an evaporation processto evaporate the material to be deposited in a processing region. In oneimplementation, the material to be evaporated is a metal or a metaloxide. In one implementation, the material to be evaporated is chosenfrom the group of aluminum (Al), zirconium (Zr), hafnium (Hf), niobium(Nb), tantalum (Ta), titanium (Ti), yttrium (Y), lanthanum (La), silicon(Si), boron (B), silver (Ag), chromium (Cr), copper (Cu), indium (In),iron (Fe), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba),nickel (Ni), tin (Sn), ytterbium (Yb), lithium (Li), calcium (Ca) orcombinations thereof. In another implementation, the material to beevaporated is chosen from the group of zirconium oxide, hafnium oxide,silicon oxide, magnesium oxide, titanium oxide, tantalum oxide, niobiumoxide, lithium aluminum oxide, barium titanium oxide, or combinationsthereof. In one implementation, the material to be deposited is a metalsuch as aluminum. Further, the evaporation material may also be an alloyof two or more metals. The evaporation material is the material that isevaporated during the evaporation and with which the microporousion-conducting polymeric substrate is coated. The material to bedeposited (e.g., aluminum) can be provided in a crucible. The materialto be deposited, for example, can be evaporated by thermal evaporationtechniques or by electron beam evaporation techniques. In anotherimplementation, the material to be deposited is deposited using chemicalvapor deposition (CVD) or atomic layer deposition (ALD) techniques. Forexample, in one implementation, the material to be deposited is Al₂O₃,which is deposited by an ALD process. In another example, the materialto be deposited is SiO₂, which is deposited by a CVD process.

In some implementations, the material to be evaporated is fed to thecrucible as a wire. In this case, the feeding rates and/or the wirediameters have to be chosen such that the desired ratio of theevaporation material and the reactive gas is achieved. In someimplementations, the diameter of the feeding wire for feeding to thecrucible is chosen between 0.5 mm and 2.0 mm (e.g., between 1.0 mm and1.5 mm). These dimensions may refer to several feedings wires made ofthe evaporation material. In one implementation, feeding rates of thewire are in the range of between 50 cm/min and 150 cm/min (e.g., between70 cm/min and 100 cm/min).

The crucible is heated in order to generate a vapor, which reacts withthe reactive gas and/or plasma supplied at operation 340 to coat thesecond surface 134 of the porous polymeric substrate 131 with a secondceramic-containing layer such as the second ceramic-containing layer138. Typically, the crucible is heated by applying a voltage to theelectrodes of the crucible, which are positioned at opposite sides ofthe crucible. Generally, according to implementations described herein,the material of the crucible is conductive. Typically, the material usedas crucible material is temperature resistant to the temperatures usedfor melting and evaporating. Typically, the crucible of the presentdisclosure is made of one or more materials selected from the groupcomprising, consisting of, or consisting essentially of metallic boride,metallic nitride, metallic carbide, non-metallic boride, non-metallicnitride, non-metallic carbide, nitrides, titanium nitride, borides,graphite, TiB₂, BN, B₄C, and SiC.

The material to be deposited is melted and evaporated by heating theevaporation crucible. Heating can be conducted by providing a powersource (not shown) connected to the first electrical connection and thesecond electrical connection of the crucible. For instance, theseelectrical connections may be electrodes made of copper or an alloythereof. Thereby, heating is conducted by the current flowing throughthe body of the crucible. According to other implementations, heatingmay also be conducted by an irradiation heater of an evaporationapparatus or an inductive heating unit of an evaporation apparatus.

In some implementations, the evaporation unit is typically heatable to atemperature of between 1,300 degrees Celsius and 1,600 degrees Celsius,such as 1,560 degrees Celsius. This is done by adjusting the currentthrough the crucible accordingly, or by adjusting the irradiationaccordingly. Typically, the crucible material is chosen such that itsstability is not negatively affected by temperatures of that range.Typically, the speed of the porous polymeric substrate 131 is in therange of between 20 cm/min and 200 cm/min, more typically between 80cm/min and 120 cm/min such as 100 cm/min. In these cases, the means fortransporting should be capable of transporting the substrate at thosespeeds.

Optionally, at operation 340, the evaporated material is reacted with areactive gas and/or plasma to form the second ceramic-containing layer,such as the second ceramic-containing layer 138, on a second surface,such as second surface 134 of the porous polymeric substrate. Accordingto some implementations, which can be combined with otherimplementations described herein, the reactive gases can be selectedfrom the group comprising, consisting of, or consisting essentially of:oxygen-containing gases, nitrogen-containing gases, or combinationsthereof. Examples of oxygen-containing gases that may be used with theimplementations described herein include oxygen (O₂), ozone (O₃), oxygenradicals (O*), or combinations thereof. Examples of nitrogen containinggases that may be used with the implementations described herein includeN₂, N₂O, NO₂, NH₃, or combinations thereof. According to someimplementations, additional gases, typically inert gases such as argoncan be added to a gas mixture comprising the reactive gas. Thereby, theamount of reactive gas can be more easily controlled. According to someimplementations, which can be combined with other implementationsdescribed herein, the process can be carried out in a vacuum environmentwith a typical atmosphere of 1*10⁻² mbar to 1*10⁻⁶ mbar (e.g., 1*10⁻³mbar or below; 1*10⁻⁴ mbar or below).

In some implementations where the evaporated material is reacted withplasma, the plasma is an oxygen-containing plasma. In oneimplementation, the oxygen-containing plasma is formed from anoxygen-containing gas and optionally an inert gas. The oxygen-containinggas may be selected from the group of N₂O, O₂, O₃, H₂O, and combinationsthereof. The optional inert gas may be selected from the group ofhelium, argon, or combinations thereof. In one implementation, theoxygen-containing plasma is formed by a remote plasma source anddelivered to the processing region to react with the evaporated materialand form the second ceramic-containing layer. In another implementation,the oxygen-containing plasma is formed in-situ in the processing regionand reacted with the evaporated material in the processing region toform the second-ceramic-containing layer.

In some implementations, the evaporated material is deposited directlyon the second surface, such as second surface 134 of the porouspolymeric substrate to form the second ceramic-containing layer, such asthe second ceramic-containing layer 138. For example, in someimplementations, where the material to be evaporated is a metal oxide,the material to be deposited is deposited on the second surface 134without the optional reactive gas/plasma treatment of operation 340.

At operation 350, an optional post-deposition treatment of the depositeddielectric layer is performed. The optional post-deposition treatmentmay include a post-deposition plasma treatment to densify the depositeddielectric layer, additional “functionalization” processes may beperformed post-deposition; for example, complete oxidation of AlO_(x) toform Al₂O₃, or deposition of polymer material to enhance punctureresistance of the membrane.

FIG. 4A illustrates a cross-sectional view of another ceramic-coatedseparator 430 formed according to one or more implementations describedherein. FIG. 4B illustrates an exploded cross-sectional view of aportion of the ceramic-coated separator 430 depicted in FIG. 4A. FIG. 5illustrates a process flow chart summarizing one implementation ofanother method 500 for forming an electrode structure according toimplementations described herein. The method 500 corresponds to thefabrication of the ceramic-coated separator 430 depicted in FIGS. 4A and4B. The ceramic-coated separator 430 is similar to the ceramic-coatedseparator 130 except that the ceramic-coated separator 430 has a secondceramic-containing layer 438 that is formed by a multi-pass process.

At operation 510, a porous polymeric substrate, such as the porouspolymeric substrate 131, having a first ceramic-containing layer, suchas the first ceramic-containing layer 136, formed on a first surface,such as the first surface 132 of the porous polymeric substrate isprovided.

At operation 520, the porous polymeric substrate 131 is optionallyexposed to a cooling process. In one implementation, the porouspolymeric substrate 131 may be cooled to a temperature between −20degrees Celsius and room temperature (i.e., 20 to 22 degrees Celsius)(e.g., −10 degrees Celsius and 0 degrees Celsius). In someimplementations, the porous polymeric substrate 131 may be cooled bycooling the processing drum over which the microporous ion-conductingpolymeric substrate travels over during processing. Other active coolingmeans may be used to cool the microporous ion-conducting polymericsubstrate. During the evaporation process, the porous polymericsubstrate 131 may be exposed to temperatures in excess of 1,000 degreesCelsius thus it is beneficial to cool the porous polymeric substrate 131prior to the evaporation process of operation 330.

At operation 530, a first portion 440 a of the second ceramic-containinglayer 438 is formed on the second surface 134 of the porous polymericsubstrate. The first portion 440 a of the second ceramic-containinglayer 438 is formed via an evaporation process as described in operation330 and/or operation 340 of FIG. 3 . The first portion 440 a may includeany of the ceramic materials disclosed herein. In one implementation,the first portion 440 a has a thickness in a range from about 1nanometer to about 50 nanometers, for example, in a range from about 15nanometers to about 50 nanometers; or in a range from about 20nanometers to about 30 nanometers.

At operation 540, the porous polymeric substrate 131, having the firstportion 440 a of the second ceramic-containing layer 438, is optionallyexposed to a cooling process. The cooling process of operation 540 maybe performed similarly to the cooling process of operation 520.

At operation 550, a second portion 440 b of the secondceramic-containing layer 438 is formed on the first portion 440 a of thesecond ceramic-containing layer 438. The second portion 440 b of thesecond ceramic-containing layer 438 is formed via an evaporation processas described in operation 330 and 340 of FIG. 3 . The second portion 440b may include any of the ceramic materials disclosed herein. In oneimplementation, the second portion 440 b has a thickness in a range fromabout 1 nanometer to about 50 nanometers, for example, in a range fromabout 15 nanometers to about 50 nanometers; or in a range from about 20nanometers to about 30 nanometers.

At operation 560, the porous polymeric substrate 131, having the firstportion 440 a and the second portion 440 b of the secondceramic-containing layer 438 is optionally exposed to a cooling process.The cooling process of operation 560 may be performed similarly to thecooling processes of operation 520 and operation 530.

At operation 570, a third portion 440 c of the second ceramic-containinglayer 438 is formed on the second portion 440 b of the secondceramic-containing layer 438. The third portion 440 c of the secondceramic-containing layer 438 is formed via an evaporation process asdescribed in operations 330 and 340 of FIG. 3 . The third portion 440 cmay include any of the ceramic materials disclosed herein. In oneimplementation, the third portion 440 c has a thickness in a range fromabout 1 nanometer to about 50 nanometers, for example, in a range fromabout 15 nanometers to about 50 nanometers; or in a range from about 20nanometers to about 30 nanometers.

In one implementation, the first portion 440 a, the second portion 440b, and the third portion 440 c comprise the same or similar ceramicmaterials. For example, the first portion 440 a, the second portion 440b, and the third portion 440 c comprise porous AlO_(x)/Al₂O₃. In anotherimplementation, at least two of the first portion 440 a, the secondportion 440 b, and the third portion 440 c comprise different ceramicmaterials. For example, the first portion 440 a comprises porousAlO_(x)/Al₂O₃, the second portion 440 b comprises porous SiO₂, and thethird portion 440 c comprises ZrO₂. It should be understood thatalthough three layers 440 a-c are depicted in FIG. 4B, any number oflayers may be deposited in order to achieve the desired thickness andproperties of the second ceramic-containing layer 438.

FIG. 6A illustrates a schematic top view of an evaporation apparatus 600for forming a ceramic-coated separator according to implementationsdescribed herein. FIG. 6B illustrates a schematic front view of theevaporation apparatus 600 shown in FIG. 6A. FIG. 6C illustrates aschematic top view of the evaporation apparatus 600 shown in FIG. 6A.The evaporation apparatus 600 may be used to form the ceramic-coatedseparator as described herein. The evaporation apparatus 600 may be usedto perform the method 300 and the method 500 as described herein. Forexample, the evaporation apparatus may be used to deposit an ultra-thinceramic-coating, for example, the second ceramic-containing layer 138,on a flexible conductive substrate, for example, the porous polymericsubstrate 131, having a thick ceramic-containing layer 636, for example,the first ceramic-containing layer 136, formed thereon.

In some implementations, as shown in FIGS. 6A and 6B, the evaporationapparatus 600 includes a first set 610 of evaporation crucibles alignedin a first line 620 along a first direction, e.g. along the x-directionshown in FIG. 6A, for generating a cloud 651 of evaporated material tobe deposited on a flexible substrate 660. In one implementation, theflexible substrate 660 includes a porous polymeric substrate 631, forexample, the porous polymeric substrate 131, having a thickceramic-containing layer 636, for example, the first ceramic-containinglayer 136, formed thereon.

With exemplary reference to FIG. 1 , typically the flexible substrate660 moves in the y-direction during the deposition process. The firstset 610 of evaporation crucibles shown in FIG. 6A includes crucibles 611to 617. Further, as exemplarily shown in FIG. 6C, the evaporationapparatus 600 includes a gas supply pipe 630 extending in the firstdirection and being arranged between the first set 610 of evaporationcrucibles and a processing drum 670. As shown in FIG. 6C, typically thegas supply pipe 630 includes a plurality of outlets 633 for providing agas supply directed into the cloud 651 of evaporated material. Further,as indicated by the double arrows in FIG. 6B, the evaporation apparatusis configured such that a position of the plurality of outlets isadjustable for changing a position of the gas supply directed into thecloud 651 of evaporated material.

Accordingly, it is to be understood that the evaporation apparatus 600as described herein may be an evaporation apparatus for a reactiveevaporation process. In some implementations, the herein describedcrucibles may be adapted for providing evaporated material on thesubstrate to be coated. For example, the crucibles may provide onecomponent of the material to be deposited as a layer on the substrate.In particular, the crucibles described herein may include a metal, e.g.aluminum, which is evaporated in the crucibles. Further, the evaporatedmaterial from the crucibles may react with a further component, e.g. areactive gas such as oxygen and/or a plasma such as an oxygen-containingplasma, in the evaporation apparatus for forming a ceramic-containinglayer as described herein on the flexible substrate. Accordingly, thealuminum from the crucibles together with the oxygen and/oroxygen-containing plasma as described herein may form a layer of AlOx,Al₂O₃, and/or a mixed layer of Al₂O₃/AlO_(x) on the flexible substratein the evaporation apparatus according to implementations describedherein. In view of the implementations described herein, the skilledperson understands that any material, specifically any metal, may beused as material in the crucibles as long as the vapor pressure of thematerial may be achieved by thermal evaporation.

During processing, the flexible substrate 660 is subjected to thematerial evaporated by the crucible set 610 as indicated by the cloud651 of evaporated material, as exemplarily shown in FIG. 6B. Further,during processing, a gas supply and/or plasma is directed into the cloud651 of evaporated material, such that a portion of the evaporatedmaterial may react with the supplied gas and/or plasma. Accordingly, theflexible substrate 660 is further subjected to evaporated material,which has been reacted with the supplied gas and/or plasma such thatduring processing, the flexible substrate 660 is coated with a layerincluding the material evaporated by the crucibles and the supplied gasand/or plasma, for example, in the form of reactive products of thecomponents provided by the crucible and the gas supply pipe.

In summary, some of the benefits of the present disclosure, include theefficient formation of a thin polymer separator stack. The thin polymerseparator stack includes an ultra-thin ceramic coating formed on a firstside of front side of the thin polymer separator, which suppressesthermal shrinkage while maintaining the desired ionic conductivity. Theultra-thin ceramic coating may be deposited using PVD techniques atelevated temperatures. The thin polymer separator stack further includesa thick ceramic coating formed on a second side or backside of the ofthe thin polymer separator, which provides mechanical stability whilemaintaining the desired ionic conductivity. Thus, the thin polymerseparator stack includes the benefit of reduced thermal shrinkage withimproved mechanical stability while maintaining desired ionicconductivity at a decreased separator thickness (e.g., 12 microns orless).

When introducing elements of the present disclosure or exemplary aspectsor implementation(s) thereof, the articles “a,” “an,” “the” and “said”are intended to mean that there are one or more of the elements.

The terms “comprising,” “including” and “having” are intended to beinclusive and mean that there may be additional elements other than thelisted elements.

The term “about” generally indicates within±0.5%, 1%, 2%, 5%, or up to±10% of the indicated value. For example, a pore size of about 10 nmgenerally indicates in its broadest sense 10 nm±10%, which indicates9.0-11.0 nm. In addition, the term “about” can indicate either ameasurement error (i.e., by limitations in the measurement method), oralternatively, a variation or average in a physical characteristic of agroup (e.g., a population of pores).

The term “crucible” as used herein shall be understood as a unit capableof evaporating material that is fed to the crucible when the crucible isheated. In other words, a crucible is defined as a unit adapted fortransforming solid material into vapor. Within the present disclosure,the term “crucible” and “evaporation unit” are used synonymously.

The term “processing drum” as used herein shall be understood as aroller, which is used during processing of a flexible substrate asdescribed herein. In particular, a “processing drum” is to be understoodas a roller, which is configured to support a flexible substrate duringprocessing. More specifically, the processing drum as described hereinmay be arranged and configured such that the flexible substrate, e.g. afoil or a web, is wound around at least a part of the processing drum.For instance, during processing, typically the flexible substrate is incontact with at least a lower portion of the processing drum. In otherwords, during processing, the flexible substrate is wound around theprocessing drum such that the flexible substrate is in contact with alower portion of the processing drum and the flexible substrate isprovided below the processing drum.

The term “gas supply pipe” is to be understood as a pipe arranged andconfigured for providing a gas supply into a space between anevaporation crucible, particularly a set of evaporation crucibles, and aprocessing drum. For instance, the gas supply pipe may be positionedand/or shaped to direct a gas supply into a cloud of evaporated materialbetween a first set of evaporation crucibles and the processing drum.Typically, the gas supply pipe includes openings or outlets, which arearranged and configured such that the gas supply from the gas supplypipe can be directed into the cloud of evaporated material. Forinstance, the openings or outlets may have at least one shape selectedfrom the group consisting of a circular shape, a rectangular shape, anoval shape, a ring-like shape, a triangular-like shape, a polygon-likeshape, or any shape suitable for delivering gas into the cloud ofevaporated material.

While the foregoing is directed to implementations of the presentdisclosure, other and further implementations of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A separator, comprising: a polymer substrate, capable of conductingions, having a first surface and a second surface opposing the firstsurface; a first ceramic-containing layer, capable of conducting ions,formed on the first surface; and a second ceramic-containing layer,capable of conducting ions, formed on the second surface, wherein thesecond ceramic-containing layer is a binder-free ceramic-containinglayer and has a thickness in a range from about 1 nanometer to about1,000 nanometers.
 2. The separator of claim 1, wherein the polymersubstrate is a microporous ion-conducting polymeric layer.
 3. Theseparator of claim 1, wherein each of the first ceramic-containing layerand the second ceramic-containing layer independently comprises amaterial selected from porous aluminum oxide, porous-ZrO₂, porous-HfO₂,porous-SiO₂, porous-MgO, porous-TiO₂, porous-Ta₂O₅, porous-Nb₂O₅,porous-LiAlO₂, porous-BaTiO₃, ion-conducting garnet, anti-ion-conductingperovskites, porous glass dielectric, or combinations thereof.
 4. Theseparator of claim 1, wherein the first ceramic-containing layercomprises a binder.
 5. The separator of claim 1, wherein the secondceramic-containing layer has a thickness in the range from about 50nanometers to about 500 nanometers.
 6. The separator of claim 1, whereinthe first ceramic-containing layer has a thickness in the range fromabout 1,000 nanometers and 5,000 nanometers.
 7. The separator of claim1, wherein the polymer substrate has a thickness in a range from about 3microns to about 25 microns.
 8. The separator of claim 1, wherein thepolymer substrate is a polyolefenic membrane.
 9. The separator of claim8, wherein the polyolefinic membrane is a polyethylene membrane or apolypropylene membrane.
 10. The separator of claim 1, wherein the secondceramic-containing layer comprises porous aluminum oxide.
 11. Theseparator of claim 10, wherein the second ceramic-containing layerfurther comprises zirconium oxide, silicon oxide, or combinationsthereof.
 12. The separator of claim 1, further comprising a thirdceramic-containing layer disposed on the second ceramic-containinglayer.
 13. The separator of claim 12, wherein the thirdceramic-containing layer comprises silicon oxide.
 14. The separator ofclaim 12, wherein the third ceramic-containing layer is binder-free. 15.The separator of claim 12, wherein the third ceramic-containing layerhas a thickness in a range from about 1 nanometer to about 100nanometers.
 16. The separator of claim 1, further comprising a fourthceramic-containing layer disposed on the third ceramic-containing layer.17. The separator of claim 16, wherein the fourth ceramic-containinglayer comprises zirconium oxide, is binder-free, and has a thickness ina range from about 1 nanometer to about 100 nanometers.
 18. A separator,comprising: a polymer substrate, capable of conducting ions, having afirst surface and a second surface opposing the first surface; a firstceramic-containing layer, capable of conducting ions, formed on thefirst surface, wherein the first ceramic-containing layer has athickness in a range from about 1,000 nanometers to about 5,000nanometers; a second ceramic-containing layer, capable of conductingions, formed on the second surface, wherein the secondceramic-containing layer is a binder-free ceramic-containing layer andhas a thickness in a range from about 1 nanometer to about 1,000nanometers; and a third ceramic-containing layer disposed on the secondceramic-containing layer.
 19. The separator of claim 18, wherein thethird ceramic-containing layer is binder-free and has a thickness in arange from about 1 nanometer to about 100 nanometers.
 20. A separator,comprising: a polymer substrate, capable of conducting ions, having afirst surface and a second surface opposing the first surface; a firstceramic-containing layer, capable of conducting ions, formed on thefirst surface; a second ceramic-containing layer, capable of conductingions, formed on the second surface, wherein the secondceramic-containing layer is a binder-free ceramic-containing layer; anda third ceramic-containing layer disposed on the secondceramic-containing layer, wherein the third ceramic-containing layer isbinder-free.